Objectives: 1. Further studies on the molecular structure of the enzyme, in particular various factors responsible for interconversion of the enzyme to different molecular size classes. 2. Fragmentation of ribonuclease chemically and enzymatically to determine the portion of the molecule which acts as substrate. 3. Reduction of unstable protein-methyl esters which are enzymatic products to corresponding hydroxy amino acid residues. 4. Investigation of protein methylase II systems in different transplantable pituitary tumors: (a) the level of the enzyme activity (b) natural inhibition for the reaction (c) molecular properties of the enzyme.